Previously Python code would require the hacky `AssetHandle` type and
query the ID type through the file data it contained (like
`asset_handle.file_data.id_type`). We want to get rid of `AssetHandle`.
With this commit we can change asset shelf methods like
`AssetShelf.asset_poll()` to take an `AssetRepresentation` instead of
`AssetHandle`, since the ID type is currently the only relevant part.
This is much nicer and won't require breaking compatibility in future to
deprecate `AssetHandle`.
d421ebac5e